Power Supply Assembly and Distribution.

TM 32-5811-024-14&P

5-5. Power Supply Assembly and Distribution.

(See figure FO-2.) The power supply assembly accepts 3-0, 115-V ac external power and provides +5-, -10-, and

+15-V ac operating power for the card cage CCAs and for the unit under test. When pressed, front-panel POWER switch

S21 energizes relay K4, transferring external ac and dc power to the power supply assembly and to the unit under test

(+28 V to the unit under test only). CB2 provides 2.5 A overcurrent protection for the external ac course, and CB1

protects the external dc power source from a unit-under-test load that draws an excess of 15 A.

The power supply assembly consists of five identical rectifier modules (VR1 thru VR5), five identical preregulator

modules (VR6 thru VR10), five identical high-frequency (HF) oscillator modules (G1 thru G5), and 11 special-purpose

output regulators (VR11 thru VR21). A typical power supply string consists of a rectifier module to convert 1 0 ac to

nonregulated dc, a preregulator to provide regulated +80 V dc to the oscillator module, and output regulators that convert

HF oscillator output into the operating voltages required by the card cage CCAs and the unit under test.

Three relays (K1, K2,and K3) are activated by the 115-V ac phase input, transferring dc operating voltages to the unit

under test. Phase 3 is selected as a requisite for outputting dc operating voltages because the ac drives the unit-under-

test cooling blower motors. Should the blowers become inoperative because of an ac power failure, the unit under test

will not operate or overheat, since operating (dc) power is not provided. Relay K1 transfers +15-V and +5-V dc power to

the unit under test via J7 and J14, and transfers -10-V and +5-V dc power via K2 and connector J14. Relay K3 transfers

+28 , dc to the df display when ac power is applied.

5-6. Front-Panel Assembly.

(See figure FO-3.) The front-panel assembly houses the control switches and power supply circuit breakers. The

control switches permit the operator to select the various test functions provided by the digital processor test set. (See

Chapter 3 for operator controls, indicators and connectors functions.)

5-2